I think that GPC is a GREAT idea. I have thought about it for weeks and weeks. I think that it would be incredibly useful for the reasons stated by the author.
I think that encryption would be useful for text files that you'd want to keep secret. Obviously, you could also encrypt pictures, but unless you like black and white low resolution porno, there's no need for that.
I'd be interested in working on a projects like these if anyone wanted to start a "group" or "team" of people to work on them. I don't know much about assembly but I sell web pages, and I'd love to make a real nice one for the makers of TI stuff (including GPC and encryption). (<-for free)

Another interesting point would be that is should change a lot--If it wasn't a key type program, and the teacher had a calc and pluged yours in and used the same encrypter/decrypter you used, she could read it. A simple way to defeat it....after all, if you can get it, your teacher can get it to, right?

Nifty - a GPC would be darn useful.
I agree with your point - it must be so that some of the key is stored in the memory of the individual. It wouldn't be too hard to take, say, the lower bits of the key, and transform it into an 8-character string. Certainly less secure than the whole key, but if the teacher confiscates your TI, you're pretty screwed already.

I must say that I am truly fascinated by your suggestions involving number theory based cryptography applications on the calculator. However, I don't think the applications you describe are really the best possible use of this technology. Passing notes on your calculator does seem, well, juvenile (kind of reminds me of the days when my school issued everyone in algebra classes a TI-81... sigh...). I'm not saying that the development of a calculator based cryptography platform is a bad idea, but it seems that a full scale platform with public keys and the like would never be used to its full extent, considering that:
1. Most of the population would not understand or simply would not see the advantage in using the program.
2. A relatively small percentage of TI calc owners use the models that would have the power/memory to support encryption/decryption. (I figure only the 92 series, the 85/86 series, and the forthcoming 89 could really handle it well).
3. If you were to use your calculator as a means of regular message transfer, it would be foolish to use it for matters that require such high security.
Once again, I am not saying that Calc Crypto is a bad idea. It's just that realistically its shortcomings on the TI calc platform would hinder its usage to the point that most people wouldn't bother.

By the way, this is my first post to ticalc.org, so I appologize if I stepped over the line or anything.

<<I must say that I am truly fascinated by your suggestions involving number theory based cryptography applications on the calculator. >>
Thank you.
<<However, I don't think the applications you describe are really the best possible use of this technology. Passing notes on your calculator does seem, well, juvenile (kind of reminds me of the days when my school issued everyone in algebra classes a TI-81... sigh...).>>
I agree too. I don't advocate the passing of notes, but then again, it was 3 AM, and I was half-asleep. That's how I write all my articles. :-D
<< I'm not saying that the development of a calculator based cryptography platform is a bad idea, but it seems that a full scale platform with public keys and the like would never be used to its full extent, considering that: >>
Of course not, but it would have its uses.
<<1. Most of the population would not understand or simply would not see the advantage in using the program. >>
No, they would not. However, many people do love "secret decoder rings" and the like.
<<2. A relatively small percentage of TI calc owners use the models that would have the power/memory to support encryption/decryption. (I figure only the 92 series, the 85/86 series, and the forthcoming 89 could really handle it well). >>
Exactly. The TI-92 and 92+ definitely could handle it. A port of the program and functions to the 89 would also be possible. However, the 85 and the 86 probably do not have the capabilites to support public key encryption.
<<3. If you were to use your calculator as a means of regular message transfer, it would be foolish to use it for matters that require such high security. >>
Yes, but how much security does a high schooler need? PGP is availiable for industrial-strength uses. Calculator Encryption would be medium strength.
<<Once again, I am not saying that Calc Crypto is a bad idea. It's just that realistically its shortcomings on the TI calc platform would hinder its usage to the point that most people wouldn't bother. >>
But some would.
<<By the way, this is my first post to ticalc.org, so I appologize if I stepped over the line or anything. >>
Nah, it's kewl. Way to go.
:-D

I still have my TI-81

Actually, why not make a 'ZIP' utitlity. You could use something like this to store MORE games and othe crap on your calc! I'd like that =) I don't know what other uses you might find for this except to shrink games but that's really just up to the programmers out there. Programs like Mathew Shepcar's 'Bloat' for the 86 provides some compression. But the idea of making a full scale encryption/compression program could be usefull for some of these ideas.

thats all it is win zip for a calculator (plus the code stuff)

Please, man, read the article BEFORE you post, not after. Calculator Encryption and a GPC would be two separate programs. Not only that, but WinZip - argh, you newbie. Call it PKZip, it was the first utility, before WinZip, a GPC would be PKZip for a calculator. *sigh*

Nah, TIZip!
PK is from the guy who designed it, Phil Katz.

Actually, I think general compression has been tryed befor, with not to good of results. The problem is that it is much harder to compress the randomness of a program. Text on the other hand is fairly easy allowing the compression algorithms to be much smaller, which is important because whats the point of getting compression to double memory, when the actuall program takes up half of it anyway?

As for practicality, there really is none. But, it could be an interesting exercise in programming/and encryption methods. I'd be very interested in seeing how it is done. Encryption has always held a slight fascination w/ me. When I made a simple encryption program on my 83 in basic to keep people outa my games, I used a method with matices to do it (I think it's taught in some math books, that's where I learned it). So, I'd be more than happy to at least see the method posted. Who knowns, maybe it'll even make a nice little project on the side to work on in assembly.

Every programmer seems to fancy himself a cryptographer, and without exception, if they haven't had training IN cryptography, they outright suck. This program would be only for the TI-92 and 92+ (a port for the 89 is possible, but I sure wouldn't do it, I have no 89.) I am using a well-known public-key method, purely mathematical, and it will be in TI-Basic. NOT assembler. The required number theory functions are not available in assembler, and I can't code assembler. :-D

Nobody that can understand cryptography has any friends worth passing notes to.

No, but the nonexistant notes are darn secure.

Wow, permutations of my initals. Ha ha ha.

There aer two encryption programs I know of, both are found in the 85 basic/ Programs archive.

encrypt.zip- for encrypting messages using a continuously changing encrypter/decrypter

rsa.zip- RSA encryption system for numbers

Dude, you need to get to sleep earlier.

Dude, I know I have to get to sleep earlier.

Come on people. If you really need to tell someone something, you can wait 60 minutes when the period is over and catch them in the hallway. And, you dont need to hide your message on a calc IR link or no. Also, Teachers are not going to go take your calc, plug it in to his or hers then decript your magical message. Teachers dont really care that much. Just setten' you right.

A stuffing program would be very very good. Having 50k on a Ti-85 without a E2 is a really cool thing (with E2 something like 1 MB). I would use a stuffing thing allot if it was made.

my teachers do whenever they catch us passing notes the make huge copys of them and put them on the wall this would solve our problem

p.s. who ever makes it please port it to the 83

Maybe your teachers don't care, but if my teachers saw me passing notes or even using my calc, they will take it and keep it till the end of the year(the calc I mean). They will also read the note to the class and all the standard stupid stuff. With the encryption, they wouldn't have a good reason to take my calc. When they see the encrypted message on the calc, I could just say it crashed or something. Since my teachers are all mentally deficient it would be a good excuse too.

To the person a couple back -
I will make Calculator Encryption, I have decided that. However, this is what I will NOT do:
Port it to any calculator besides the 89. And even that's doubtful.

This is precisely to STOP people like you. I do not advocate the passing of notes, but a good RSA encryption program is needed. By making it for the TI-92, only advanced math students will have access to it. By the way, any calculator BUT the TI-92 and 89 would not have the capability to run it, the mathematics required is too intense.

Sorry, but I'm a nerd. And as a rule, I don't advocate unnerdly things. :-D

Now, to the person immediately before me:
Yes, I see your point. However, I do admit it won't be THAT useful. But it will be, slightly.